Process for removing tellurium from antimony



Patented Dec. 1, 1953 s tar-rags; swam oram E 21 2,661,280; P REM IN LILLUBHIMQ Fnplig minnow Yurii j Lelgedefir Metuchen, and "William- C.--

Kle im- Menlo Parkg N. J., assigiiors toAmel-ican Smelti-ngvoandsRefining Company. New York; NQLYT; a cclsporation of NewvJerseys NgDrawing Application September 15, 1951;

SeriajlfIo. 246,874

6 fila ignsce (o1. 35, 69

This-invention-;-rel ates to the removalof -tellu rium fiom. antimony. 5

An important object of the invention is-:to-p1=o-- vigie a simple, efficient and economical-process for removing tellurium from antim-ony containin'g telliiri-um as an impuritywithout removing appreciable quantities of; antimony -wi th:- the tel.-. luriti m an d jui'ther' tmprovidea process-forwpre-s paring; antimonyhaying a low tellurium content.

Klthoug'h the novel features wh-ich are-believed to-becharajcteristicof this invention wi-l-l bepare tiula-rlyf pointed out nin theclaims appended hereto,the invention itself as to itsmbiects-and adyanta'ges} and-the manner in which -it- -may. .be t

carried-out may be; better understood by, reference to the iollow ingdescription-.--

It =has been foun'd fthat tellur-ium contained lino. antimony can; be l-emptied therefrom by melting .o theantimony in -a refractory vessel; incorporate ing an alkali' metal-reagent infthemelt;forminga s'lagof the alkali--metal- -reagentcontaining J telIuriu m, andlseparatingtheslag from the body; of the -anti'monyf. 'The allgali metal reagent-can bemost effectively and economieallyaincorpoas rated into "the; melt by -treatingthe liquidsmetals with a molten reducible alkali metal-ecompoundvv in the presenceofa red-using agent. The.v alkali 1 metal compound qeacts rapidly inthe apresencea 0fthereduoing--agent withw'the tel-lur-ium=in,=the..

antimony to form a slag containing telluriuma The s1ag-may be readily removed fromilthe antimony by skimming from -the.surface,- thereby:

purityi'ngj'the antimony with respectato the telfi um-r mm's --also weenfound that-the telluriumains the slag is continuously volatilized' therefromtasi.

the process proceedsand that the-more-prolonged the treatment theugreaten-theamount 'ofmtellu s rium removed from the -s1ag.- The volatilized tellurium. is proloahly in the form of tellurium This, ieature is .advantageous particularly it/hen treating antimony containing a rela- As stated. earlierythe lreactionsbetweenl the; re; clucedualkalil metal landsthe tellurium in thegan timony is: sufiiciently rapidmso 1 thatlthe tellurium is remdi' -ed from-theantimony into. the slag.in a

par ted t9 tains a major portion of t he telluriurn remojed,

from the antimony, although a slag may also be removed which contains a minor portion of the 1:. e,-;c mm9nd in a e ts: su h-1 .1 1 P k o l-fihl qalimabe e i t e p o sim si -h en w$ .1m at the 15.31.0123? aq z as'.s i llaanaww as s ari cu a s a ta s us au s-t eses m y. be u o s e ateihs. ma-ten ant m m y b b n i r u h he. -m9lte lme alvandea heisame me mmv a he uc n ,ra sntiq lt esr act on -b tw n the lly 'u gan eredupib eac pounqh a er t-tri i ate a es ihxdrQ epzo a ib d o gas that is readily availaple may be used n case a solid reducing agent is used it is added to the surface of the molten metal and mechanical; agitation:aoi-sthe meta ,eredupin je entran alkali meta-1 s mpoun iis' provided! ecausest y ar o A a on l zc s ian-ulmvewm ltinazpqints that an... low-enou h: forms? mit pro es .v ukthe r xides carb nat s fwl hfi hfil? lk i y be used Sod hlori eo anl qo herfi "ta idr ae li1'reaaehtiu eeit i hemolten *metasb e n Y at a salt for adjustingthe melti l p ll 'i lx ffi ducible compound may be dispensed with.

The following are specific? examples of the mo deiofoperatingtheprocesa Ezpamplg I j Example ll:

Fourteen hundred pounds of antimony metal containing .68% tellurium was melted in a suit- 3 able container to 1300 F. and 25 lbs. of sodium hydroxide containing lbs. of sodium chloride was added to the surface of the molten metal. The alkali metal hydroxide rapidly became fluid whereupon natural gas was passed into the molten metal through a tube placed beneath the surface of the metal for approximately thirty minutes while the temperature of the molten metal was held in the range of 1300 to 1350 F. Approximately lbs. of slag which analyzed 6.7% Te and 12.9% Sb was then skimmed from the surface of the metal. The remaining antimony contained only .4% Te. Two additional like treatments with similar amounts of reagent reduced the tellurium content of the antimony to only .03%. Example III Fifteen hundred pounds of antimony metal containing .61% tellurium was melted in a suitable container to 1300 F. and 36 lbs. of molten potassium hydroxide was added to the molten metal. Natural gas was passed into the molten metal through a Carborundum tube placed beneath the surface of the metal for approximately thirty minutes while the temperature of the molten metal was held in the range of 1300 to 1350 F. Approximately 14 lbs. of slag was then skimmed off. The slag analyzed 5.8% tellurium. The remaining antimony contained only .46% Te. Two additional like treatments with similar amounts of reagent reduced the tellurium content of the antimony to .15%.

Example IV Fifteen hundred grams of antimony metal containing .61% tellurium was melted in a graphite crucible to 1300 F. under an atmosphere of nitrogen. Seventy-five grams of molten sodium hydroxide was added to the surface of the molten metal as a cover for the bath and as a carrier for metallic sodium. Fifty grams of metallic sodium then was added to the molten caustic. The melt under the atmosphere of nitrogen was agitated by passing nitrogen through a tube placed beneath the surface of the antimony metal; the agitation continuing for thirty minutes while the temperature of the molten metal was held in the range of 1300 to 1350 F. Approximately 125 grams of slag was then skimmed off. The slag analyzed 5% Te and the remaining antimony contained .08% Te.

Example V Fourteen hundred and eighty-eight pounds of antimony metal containing 0.64% tellurium was heated to approximately 1300 F. in a refractory container under a blanket of natural gas after which '75 lbs. of melted sodium hydroxide was added to the surface of the metal pool. The mixture was agitated by passing natural gas into the molten metal through a tube placed beneath the surface thereof for a period of ten minutes while the temperature of the metal was held in the range of 1300 to 1350 F. At the end of the ten minute period a slag containing 3.17% tellurium was skimmed from the surface of the metal. The antimony remaining after the removal of the slag was found to contain 0.2% tellurium.

The above procedure was repeated starting with 1471 lbs. of antimony metal containing 0.62% Te and using 75 lbs. of melted sodium hydroxide. The agitation with natural gas was continued for two hours, however. The slag removed at the 4 end of the two hour period was found to contain 0.9% tellurium and the remaining antimony metal contained 0.2% Te.

It will be noted that suficient tellurium was volatilized from the slag during the longer period of the second run to reduce the tellurium c0ncentration in this slag to 0.9%.

The small amount of antimony lost in the slag constitutes a particular advantage of the process. By careful control of the process it has been found that the loss of antimony may be maintained as low as 3 lbs. of antimony per pound of tellurium removed from the metal.

While the processfor removal of tellurium from antimony, has been particularly described with reference to specific reducible alkali metal compounds and certain reducing agents, the process is not limited to the specific reducing agents or reducible alkali metal compounds, temperatures or operating procedures described but may be practiced in other ways within the scope of the claims hereinafter made.

What is claimed is:

1. A process for removing tellurium from antimony which comprises establishing a pool of molten antimony metal containing tellurium and having thereon an overlying layer of molten slag, agitating said molten antimony metal pool in the presence therein of an alkali metal, discontinuing said agitation, and separating from the body of the antimony a slag containing tellurium. 2. A process according to claim 1 in which the alkali metal is formed in situ in said pool.

3. A process for removing tellurium from antimony which comprises establishing a pool. of molten antimony metal containing tellurium and having thereon an overlying layer of molten Ina-- terial comprising a reducible alkali metal compound, introducing a reducing gas beneath the surface of said molten pool thereby agitating said pool and said overlying layer, thereby also reducing said alkali metal compound and incorporating the reduced alkali metal into said pool, continuing the introduction of said reducing gas until the tellurium content of said antimony is reduced by a desired amount, thereafter discontinuing the introduction of said gas, and separating from the body of the antimony a slag containing tellurium.

4. A process according to claim 3 in which the reducing gas is natural gas.

Y 5. A process according to claim 3 in which said overlying layer comprises a member of the group consisting of alkali metal hydroxides and alkali metal carbonates.

6. A process according to claim 3 in which the separated slag contains a major portion of the tellurium removed from the antimony.

YURII E. LEBEDEFF. WILLIAM C. KLEIN.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Antimony by Chung Yu Wong, p. 135, published 1909. 

1. A PROCESS FOR REMOVING TELLURIUM FROM ANTIMONY WHICH COMPRISES ESTABLISHING A POOL OF MOLTEN ANTIMONY METAL CONTAINING TELLURIUM AND HAVING THEREON AN OVERLYING LAYER OF MOLTEN SLAG, AGITATING SAID MOLTEN ANTIMONY METAL POOL IN THE PRESENCE THEREIN OF AN ALKALI METAL DISCONTINUING SAID AGITATION, AND SEPARATING FROM THE BODY OF THE ANTIMONY A SLAG CONTAINING TELLURIUM. 